tracing: use emojis

[yoshuawuyts]

Our user timings aren't the most accessible at the moment:

They're formatted as:

choo.emit('foo') [123123]

which doesn't look too great. Instead, I was thinking we could improve our user timings by using emojis, and removing the trailing UUID. Making it closer to:

🚂 emit('foo')

Or even:

🚂 emit [foo]

🚂 emit(foo)

This should hopefully help with user timings, and making it all slightly easier to debug.

[yoshuawuyts]

Or should we keep it as:

🚂 choo.emit(foo)